Dump trailer bounces on the way down (if coming down heavy)

[nyone]

That bounce sounds a lot like air is somewhere in there. That fluid would have to be compressing and that don’t happen. Just my two cents worth

I think the same.

You may need to disconnect the cylinder and flip it upside down and cycle it to get all the air out.

 

[Sodo]

I don't know where to find a schematic but I will look.
The pump runs to power down, it seems appx the same speed up and down.
It mashes the bed hard onto the frame at bottom, and the pump stalls.

So is it feasible to add an accumulator (or some hydraulic device) on the down circuit to stop the bounce?

nyone.... you think there could be some air below the piston that cannot escape? I could perhaps reverse the trailer over a bank to tip the cylinder upward. I will look at the angles when it's "down".

 

[jmc]

I don't know where to find a schematic but I will look.
The pump runs to power down, it seems appx the same speed up and down.
It mashes the bed hard onto the frame at bottom, and the pump stalls.

So is it feasible to add an accumulator (or some hydraulic device) on the down circuit to stop the bounce?

nyone.... you think there could be some air below the piston that cannot escape? I could perhaps reverse the trailer over a bank to tip the cylinder upward. I will look at the angles when it's "down".

Low reservoir oil level might let it suck air. I've had that bounce and I've had low oil but don't remember if the two faults were related.

You don't have a schematic but do you have the manual?

Afterthought: my ez-dumper uses automatic transmisssion fluid. The reservoir level line is for when the bed is either up or down, IIRC.

 

[Mike1955]

I don't know where to find a schematic but I will look.
The pump runs to power down, it seems appx the same speed up and down.
It mashes the bed hard onto the frame at bottom, and the pump stalls.

So is it feasible to add an accumulator (or some hydraulic device) on the down circuit to stop the bounce?

nyone.... you think there could be some air below the piston that cannot escape? I could perhaps reverse the trailer over a bank to tip the cylinder upward. I will look at the angles when it's "down".

Sodo I do not think an accumulator would help your situation. That should be a simple hydraulic circuit. But it might be layed out so it’s difficult to follow. also gauges in some places would help. And don’t forget that you may be overloading that thing to. But if it isn’t air that oil is overcoming a spool valve somewhere

 

[oldnslo]

Air makes things bounce when trapped but since he is lowering air would be less likely to cause bounce since load induced pressure should not be changing significantly. Yes it would bounce like a pogo stick if you stopped lowering.

 

[Sodo]

There's no "up&down". It stutters violently. "Stick-slip" might be a better description.

 

[bcp]

Maybe something useful here:

What Causes a Hydraulic Cylinder to Chatter? - Cylinders, Inc.

Discover the causes of hydraulic cylinder chatter and learn how to fix it. Explore solutions to prevent chattering and extend your cylinder's life.

cylindersinc.com

Bruce

 

[Dave M7040]

Is there a lever or switch you operate to lower? I suspect there is some type of valve in that pump housing to lower the load and it might have some type of flow control that is acting up.

Very, very unlikely pump runs in reverse to lower.

oldnslo
E-Z dumper's web site mentions a Monarch double acting pump.
Double Acting Monarch Hydraulic Pump With 1 Quart Reservoir

Dave M7040

 

[oldnslo]

oldnslo
E-Z dumper's web site mentions a Monarch double acting pump.
Double Acting Monarch Hydraulic Pump With 1 Quart Reservoir

Dave M7040

Dave,
I suspect the double acting monarch unit is implying will work with double acting cylinders.

How would you prevent over speeding the DC motor if Running pump opposite direction to pull oil out of the cylinder especially with load induced pressure?

I will first to admit that I could be wrong.

 

[MattB4]

When was the last time you replaced the hydraulic oil?